1. Field of the Invention
One or more embodiments of the present invention relate to an antenna apparatus that is assembled into an electronic apparatus and made communicatable upon receipt of a magnetic field transmitted from a transmitter, and a communication apparatus, as well as a method for manufacturing such an antenna apparatus.
2. Background Art
In electronic apparatuses such as portable telephones or the like, an antenna module for an RFID (Radio Frequency Identification) has been used for installing a function for near non-contact communication therein.
This antenna module carries out a communication by utilizing an inductive coupling with an antenna coil mounted on a transmitter such as a reader writer or the like. That is, by allowing its antenna coil to receive a magnetic field from the reader writer, this antenna module converts it to electric power and makes it possible to drive an IC that functions as a communication processing unit.
In order to positively carry out communication, the antenna module needs to receive a magnetic flux of a predetermined value or more from the reader writer. For this reason, an antenna module in accordance with a conventional example installs a loop coil in a casing of the portable telephone, and receives the magnetic flux from the reader writer by using this coil.
However, in the antenna module assembled into an electronic apparatus such as a portable telephone or the like, because the magnetic flux from the reader writer is repelled by an eddy current that is generated by metals for use in substrates, battery packs and the like inside the apparatus, when they receive a magnetic field from the reader writer, the magnetic flux reaching the loop coil becomes smaller. As the magnetic flux reaching the loop coil becomes smaller in this manner, the antenna coil may require a loop coil having a certain degree of size for collecting required magnetic fluxes, and it may be necessary to use a magnetic sheet so as to increase the magnetic fluxes.
As described above, the magnetic flux from the reader writer is repelled by the eddy current flowing through the substrate of the electronic apparatus such as a portable telephone or the like; however, on the surface of the casing in the electronic apparatus, there is a magnetic field component directed in the in-plane direction of the substrate, and Patent Document 1 has proposed an apparatus in which, by receiving this component, a function for an antenna is exerted. More specifically, Patent Document 1 has proposed an antenna structure in which a coil is wounded around a ferrite core so as to reduce the occupied area of the coil.